Diphenylcarbazide is primarily used as a colorimetric reagent in analytical chemistry for the detection and quantification of hexavalent chromium (Cr(VI)) in environmental samples, such as water, wastewater, and soil. In an acidic medium, it reacts with Cr(VI) to form a distinctive violet-colored 1,5-diphenylcarbazone complex, which can be measured spectrophotometrically at around 540 nm. This application is crucial for water quality analysis, environmental monitoring, and regulatory compliance. It is also used for the determination of other metal ions, such as vanadium(V) and molybdenum(VI), though chromium remains the primary target. In research laboratories, it aids in studying chromium speciation and redox reactions. Note: It is not typically used as a titration indicator or in the synthesis of dyes/pigments, and its role as a stabilizer is limited.